We wish to define more precisely the relationship between blood flow and the intratissue content of metabolites (high energy phosphate compounds, lactate and pyruvate)within the same region of a heart. The results of these regionl analyses will be correlated with other types of measurements obtained from the whole heart-total blood flow, flow to inner and outer layers of the left ventricle, oxygen consumption, lactate and pyruvate uptake or release, cardiac output and parameters related to ventricular performance. Experiments will be performed in dog with normal coronary arteries and the heart will be stressed with volume overload (acute and chronic) and pressure overload. The aim is to evaluate the relationship between flow, oxygen supply and metabolism in the heart under various stresses. The ultimate goal is to try and define factors which control delivery of oxygen and factors which determine the balance between energy supply and demand of the heart. Our present evaluations of demand by the heart are imprecise in that the demand is only indirectly measured. Because we will now be focusing upon correlations of flow with metabolism, the name of the grant has been changed.